Lattice Boltzmann Simulation of a Gas-to-Solid Reaction and Precipitation Process in a Circular Tube

摘要

The lattice Boltzmann method(LBM)is used to simulate the growth of a solid-deposit on the walls of a circular tube resulting from a gas-to-solid reaction and precipitation process.This process is of particular interest for the design of reactors for the production of hydrogen by the heterogeneous hydrolysis of steam with Zn vapor in the Zn/ZnO thermochemical cycle.The solid deposit of ZnO product on the tube wall evolves in time according to the temporally-and axially-varying convective-diffusive transport and reaction of Zn vapor with steam on the solid surface.The LBM is wellsuited to solving problems with coupled flow,heat and mass transfer in a time-evolving domain.Here,a D2Q9 axisymmetric multiple-relaxation-time(MRT)lattice Boltzmann scheme is used to simulate incompressible fluid transport while a D2Q5 axisymmetric MRT lattice Boltzmann scheme is used to simulate the convective-diffusive transport of Zn vapor.The model is first validated against several analytical solutions,followed by a parametric study to understand the effect of Reynolds,Schmidt,and Damk?hler numbers on the time evolution of the ZnO deposition profile along the tube axis.The axial location of the fastest deposition is found to increase with increasing Peclet number,and decrease with increasing Damk?hler number,with no independent effect from the Schmidt number.When the reaction kinetics are assumed to increase along the tube axis due to nonisothermal tube wall temperature,a second peak in the deposition profile can be observed for sufficiently low values of Da/Pe.